The present invention relates to microwave transmission lines, and more particularly to an apparatus for transitioning between a microstrip transmission line and a ridge waveguide.
Many modern phased array antenna designs use microstrip phase shifters, which are integrated with dipoles on the same circuit. In order to test these integrated circuits in production, a test station consisting of a computer controlled network analyzer with coaxial connector test ports is utilized. This network analyzer system uses error modeling techniques to increase the accuracy of the measurements. The test station must provide a low loss, low VSWR transition from the coaxial connectors to the dipole of the integrated circuit, to minimize errors thereby increasing the accuracy of the measurements.
One previous approach was to enclose one incident (circuit under test) dipole and one receive dipole in a cutoff waveguide section. This approach was extremely sensitive to the position of the incident dipole with respect to both the receive dipole and the waveguide section. This dipole-to-dipole transition also required the insertion of the incident dipole into the waveguide, increasing the possibility of misalignment and damage to the circuit under test. The VSWR and insertion loss bandwidth obtained by a dipole-to-dipole transition used on previous test stations was on the order of 10 to 15 percent.